A Hawkes Bay couple are being treated for burns and police are still trying to ascertain how it happened.

A 42-year-old woman received burns to a large portion of her body last night at a residential property in Whakatu, north of Hastings, about 7.10pm and her 49-year-old partner was burned on his hands and arms.

The woman is in a critical condition in hospital, while her partner's condition is stable, detective senior sergeant Dave de Lange said.

Police were investigating how the incident occurred, but had not yet been able to speak to the couple.

They would be carrying out a scene examination at the Whakatu address and speaking with people who contacted emergency services to begin to establish what happened.